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| Barbraud, Christophe; Bertrand, Arnaud; Bouchon, Marilu; Chaigneau, Alexis; Delord, Karine; Demarcq, Herve; Gimenez, Olivier; Gutierrez Torero, Mariano; Gutierrez, Dimitri; Oliveros Ramos, Ricardo; Passuni, Giannina; Tremblay, Yann; Bertrand, Sophie. |
| In marine ecosystems top predator populations are shaped by environmental factors affecting their prey abundance. Coupling top predators' population studies with independent records of prey abundance suggests that prey fluctuations affect fecundity parameters and abundance of their predators. However, prey may be abundant but inaccessible to their predators and a major challenge is to determine the relative importance of prey accessibility in shaping seabird populations. In addition, disentangling the effects of prey abundance and accessibility from the effects of prey removal by fisheries, while accounting for density dependence, remains challenging for marine top predators. Here, we investigate how climate, population density, and the accessibility and... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00450/56117/57647.pdf |
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| Assene, Fernand; Morel, Yves; Delpech, Audrey; Aguedjou, Micael; Jouanno, Julien; Cravatte, Sophie; Marin, Frederic; Ménesguen, Claire; Chaigneau, Alexis; Dadou, Isabelle; Alory, Gael; Holmes, Ryan; Bourlès, Bernard; Koch-larrouy, Ariane. |
| In this paper, we analyse the results from a numerical model at high resolution. We focus on the formation and maintenance of subsurface equatorial currents in the Gulf of Guinea and we base our analysis on the evolution of potential vorticity (PV). We highlight the link between submesoscale processes (involving mixing, friction and filamentation), mesoscale vortices and the mean currents in the area. In the simulation, eastward currents, the South and North Equatorial Undercurrents (SEUC and NEUC respectively) and the Guinea Undercurrent (GUC), are shown to be linked to the westward currents located equatorward. We show that east of 20∘ W, both westward and eastward currents are associated with the spreading of PV tongues by mesoscale vortices. The... |
| Tipo: Text |
Palavras-chave: Equatorial atlantic; NEUC (North Equatorial Undercurrents); SEUC (South Equatorial Undercurrents); Vortices; Mixing; Friction. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00645/75697/76601.pdf |
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| Keppler, Lydia; Cravatte, Sophie; Chaigneau, Alexis; Pegliasco, Cori; Gourdeau, Lionel; Singh, Awnesh. |
| In the Southwest Pacific Ocean, waters transit from the subtropical gyre before being redistributed equatorward and poleward. While the mean pathways are known, the contribution to the mixing and transport of the water from mesoscale eddies has not been comprehensively investigated. In this research, satellite altimetry data, combined with an eddy detection and tracking algorithm is used to investigate the distribution and surface characteristics of mesoscale eddies in this region of complex bathymetry (10 degrees S-30 degrees S, 140 degrees E-190 degrees E). Detected eddies are then colocalized with in situ data from Argo floats to determine their vertical structure and the effect of eddies on the water masses. The numerous islands affect the eddy... |
| Tipo: Text |
Palavras-chave: Mesoscale eddies; Southwest Pacific; Argo floats; Satellite altimetry. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00489/60039/63314.pdf |
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| Passuni, Giannina; Barbraud, Christophe; Chaigneau, Alexis; Demarcq, Herve; Ledesma, Jesus; Bertrand, Arnaud; Castillo, Ramiro; Perea, Angel; Mori, Julio; Viblanc, Vincent A.; Torres-maita, Jose; Bertrand, Sophie. |
| In fluctuating environments, matching breeding timing to periods of high resource availability is crucial for the fitness of many vertebrate species, and may have major consequences on population health. Yet, our understanding of the proximate environmental cues driving seasonal breeding is limited. This is particularly the case in marine ecosystems, where key environmental factors and prey abundance and availability are seldom quantified. The Northern Humboldt Current System (NHCS) is a highly productive, low-latitude ecosystem of moderate seasonality. In this ecosystem, three tropical seabird species (the Guanay Cormorant Phalacrocorax bougainvillii, the Peruvian Booby Sula variegata, and the Peruvian Pelican Pelecanus thagus) live in sympatry and prey... |
| Tipo: Text |
Palavras-chave: Anchovy; Engraulis ringens; Guanay Cormorant; Northern Humboldt Current System; Occupancy model; Oceanographic variability; Pelecanus thagus; Peru; Peruvian Booby; Peruvian Pelican; Phalacrocorax bougainvillii; Prey abundance; Seasonal breeding; Sula variegata. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00317/42844/74394.pdf |
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| Kolodziejczyk, Nicolas; Testor, Pierre; Lazar, Alban; Echevin, Vincent; Krahmann, Gerd; Chaigneau, Alexis; Gourcuff, Claire; Wade, Malick; Faye, Saliou; Estrade, Philippe; Capet, Xavier; Mortier, Laurent; Brehmer, Patrice; Schuette, Florian; Karstensen, Johannes. |
| Glider measurements acquired along 4 transects between Cap‐Vert Peninsula and the Cape Verde archipelago in the eastern tropical North Atlantic during March‐April 2014 were used to investigate fine‐scale stirring in an anticyclonic eddy. The anticyclone was formed near 12°N off the continental shelf and propagated north‐west towards the Cape Verde islands. At depth, between 100‐400 m, the isolated anticyclone core contained relatively oxygenated, low salinity South Atlantic Central Water, while the surrounding water masses were saltier and poorly oxygenated. The dynamical and thermohaline subsurface environment favored the generation of fine‐scale horizontal and vertical temperature and salinity structures in and around the core of the anticyclone. These... |
| Tipo: Text |
Palavras-chave: Submesoscale; Stirring; Tropical Atlantic; Meoscale eddy; Glider measurements; OMZ. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00450/56162/57708.pdf |
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| Costa Da Silva, Alex; Chaigneau, Alexis; Dossa, Alina N.; Eldin, Gerard; Araujo, Moacyr; Bertrand, Arnaud. |
| Using current, hydrographic and satellite observations collected off Northeast Brazil around the Fernando de Noronha Archipelago and Rocas Atoll during two oceanographic cruises (spring 2015 and fall 2017), we investigated the general oceanic circulation and its modifications induced by the islands. In spring 2015, the area was characterized by lower SST (26.6°C) and deep mixed-layer (∼90 m). At this depth, a strong current shear was observed between the central branch of the eastward flowing near-surface South Equatorial Current and the westward flowing South Equatorial Undercurrent. In contrast, in fall 2017, SST was higher (∼28.8°C) and the mixed-layer shallower (∼50 m). The shear between the central South Equatorial Current and the South Equatorial... |
| Tipo: Text |
Palavras-chave: Mesoscale activity; Satellite data; Western tropical Atlantic; Shipboard measurements; Island wake; Central South Equatorial Current; South Equatorial Undercurrent. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00691/80290/83399.pdf |
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